xfs: Check buffer lengths in log recovery

xfs: Check buffer lengths in log recovery

Before trying to obtain, read or write a buffer,
check that the buffer length is actually valid. If
it is not valid, then something read in the recovery
process has been corrupted and we should abort
recovery.

Reported-by: Eric Sesterhenn <[email protected]>
Tested-by: Eric Sesterhenn <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Felix Blyakher <[email protected]>
Signed-off-by: Dave Chinner <[email protected]>
Signed-off-by: Felix Blyakher <[email protected]>